Resistor

ABSTRACT

A resistor includes a first insulator, a resistive body, a second insulator, a pair of electrodes, and a covering body. The first insulator has a first obverse surface facing in a thickness direction thereof. The resistive body is provided on the first obverse surface. The second insulator covers the resistive body. The pair of electrodes are electrically connected to the resistive body at both sides in a first direction perpendicular to the thickness direction. The covering body is formed on at least one of the first insulator and the second insulator. The covering body has electrical conductivity. The first layer is in contact with at least one of the first insulator and the second insulator.

TECHNICAL FIELD

The present disclosure relates to a resistor mainly used for currentdetection.

BACKGROUND ART

A resistor that includes a resistive body made of a metallic material isconventionally known. The resistor is mainly used for current detection.Patent Document 1 discloses an example of such a resistor including aresistive body. The resistor includes a resistive body, and a pair ofelectrodes connected to the respective ends of the resistor.

Detecting a larger current with the resistor increases heat generated bythe resistor. When the temperature of the resistor rises due to theheat, the resistance value of the resistor may fluctuate. It is thusnecessary to improve the heat dissipation property of the resistor.

PRIOR ART DOCUMENT

Patent Document

-   Patent Document 1: JP-A-2013-225602

SUMMARY OF THE INVENTION Technical Problem

In view of the above circumstances, an object of the present disclosureis to provide a resistor capable of improving heat dissipation property.

Solution to Problem

A resistor provided by the present disclosure includes: a firstinsulator including an obverse surface facing in a thickness direction;a resistive body arranged on the obverse surface; a second insulatorcovering the resistive body; a pair of electrodes electrically connectedto the resistive body at both sides in a first direction perpendicularto the thickness direction; and a covering body formed on at least oneof the first insulator and the second insulator, wherein the coveringbody has a first layer, the first layer including electricalconductivity and being in contact with at least one of the firstinsulator and the second insulator.

Other features and advantages of the present disclosure will becomeapparent from the detailed description given below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a resistor according to a first embodiment ofthe present disclosure;

FIG. 2 is a plan view corresponding to FIG. 1 and seen through a secondlayer of a covering body;

FIG. 3 is a plan view corresponding to FIG. 1 and seen through a firstinsulator and the covering body;

FIG. 4 is a bottom view of the resistor shown in FIG. 1;

FIG. 5 is a front view of the resistor shown in FIG. 1;

FIG. 6 is a cross-sectional view along line VI-VI of FIG. 2;

FIG. 7 is a partially enlarged view of FIG. 6;

FIG. 8 is a partially enlarged view of FIG. 6;

FIG. 9 is a partially enlarged view of FIG. 7;

FIG. 10 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 11 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 12 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 13 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 14 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 15 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 16 is a cross-sectional view illustrating a manufacturing step ofthe resistor shown in FIG. 1;

FIG. 17 is a partially enlarged cross-sectional view of a resistoraccording to a first variation of the first embodiment of the presentdisclosure;

FIG. 18 is a partially enlarged cross-sectional view of a resistoraccording to a second variation of the first embodiment of the presentdisclosure;

FIG. 19 is a plan view of a resistor (seen though a second layer of acovering body) according to a third variation of the first embodiment ofthe present disclosure;

FIG. 20 is a plan view of a resistor (seen though a second layer of acovering body) according to a fourth variation of the first embodimentof the present disclosure;

FIG. 21 is a plan view of a resistor (seen though a second layer of acovering body) according to a fifth variation of the first embodiment ofthe present disclosure;

FIG. 22 is a cross-sectional view of a resistor according to a secondembodiment of the present disclosure;

FIG. 23 is a partially enlarged view of FIG. 22;

FIG. 24 is a cross-sectional view of a resistor according to a thirdembodiment of the present disclosure;

FIG. 25 is a partially enlarged view of FIG. 24;

FIG. 26 is a plan view of a resistor according to a fourth embodiment ofthe present disclosure, and seen through a second layer of a coveringbody;

FIG. 27 is a front view of the resistor shown in FIG. 26;

FIG. 28 is a cross-sectional view along line XXVIII-XXVIII in FIG. 26;and

FIG. 29 is a partially enlarged view of FIG. 28.

MODES FOR CARRYING OUT THE INVENTION

The following describes embodiments of the present disclosure withreference to the attached drawings.

First Embodiment

With reference to FIGS. 1 to 9, a resistor A10 according to a firstembodiment of the present disclosure will be described. The resistor A10is intended for a shunt resistor used for current detection. Theresistance of the resistor A10 is approximately 5 mΩ to 220 mΩ. Theresistor A10 is surface-mounted on any of the wiring boards of variouselectronic devices. The resistor A10 includes a first insulator 11, aresistive body 20, a second insulator 12, a covering body 30, and a pairof electrodes 40. For convenience of understanding, FIG. 2 is shownthrough a second layer 32 (described below) of the covering body 30. Forconvenience of understanding, FIG. 3 is shown through the firstinsulator 11 and the covering body 30.

In the description of the resistor A10, the thickness direction of thefirst insulator 11 is referred to as a “thickness direction z” forconvenience. The direction perpendicular to the thickness direction z isreferred to as a “first direction x”. The direction perpendicular toboth of the thickness direction z and the first direction x is referredto as a “second direction y”. The “thickness direction z”, the “firstdirection x”, and the “second direction y” are also applied to thedescription of resistors A20 to A40 described below. As shown in FIG. 1,the resistor A10 is rectangular as viewed along the thickness directionz. In the resistor A10, the first direction x corresponds to thelongitudinal direction of the resistor A10 as viewed in the thicknessdirection z.

As shown in FIG. 6, the resistive body 20 is arranged on the firstinsulator 11. The first insulator 11 is a synthetic resin sheet made ofepoxy resin or the like. The first insulator 11 has electricalinsulation and flexibility. The first insulator 11 contains fillers 112that are electrically insulative. The fillers 112 are made of a materialcontaining ceramics having a relatively high thermal conductivity, suchas alumina (Al₂O₃) and boron nitride (BN).

As shown in FIG. 6, the first insulator 11 has a first obverse surface11A and a first reverse surface 11B. The first obverse surface 11A facesthe side of the thickness direction z at which the resistive body 20 isarranged with respect to the first insulator 11. The first reversesurface 11B faces opposite from the first obverse surface 11A. The firstinsulator 11 has a thickness (length from the first obverse surface 11Ato the first reverse surface 11B in the thickness direction z) of 40 μmto 60 μm.

As shown in FIG. 6, the resistive body 20 is a passive element arrangedon the first obverse surface 11A of the first insulator 11. Examples ofthe material for the resistive body include a copper (Cu)-manganese(Mn)-nickel (Ni) alloy (Manganin®), and a copper-manganese-tin (Sn)alloy (Zeranin®). The resistive body 20 has a thickness of 50 μm to 150μm. As shown in FIGS. 3 and 6, the resistive body 20 is provided with aplurality of resistive slits 21 that penetrate through in the thicknessdirection z. The plurality of resistive slits 21 are provided to set theresistance of the resistive body 20 to a predetermined value. Theplurality of resistive slits 21 extend in the second direction y. Bothends of the resistive body 20 in the second direction y are partiallyopen due to the plurality of resistive slits 21. The plurality ofresistive slits 21 cause the resistive body 20 to have a meanderingshape relative to the first direction x, as viewed along the thicknessdirection z. As shown in FIG. 7, side walls 22 of the plurality ofresistive slits 21 are recessed toward the inside of the resistive body20.

As shown in FIGS. 3 to 6, the second insulator 12 covers the resistivebody 20. The second insulator 12 is a synthetic resin sheet made ofepoxy resin or the like. The second insulator 12 has a second obversesurface 12A and a second reverse surface 12B. The second obverse surface12A faces the side of the thickness direction z at which the firstinsulator 11 is arranged with respect to the second insulator 12. Thesecond insulator 12 has a thickness (length from the second obversesurface 12A to the second reverse surface 12B in the thickness directionz) of 40 μm to 60 μm. The second obverse surface 12A is in contact withthe surface of the resistive body 20. As such, the resistive body 20 issandwiched between the second obverse surface 12A and the first obversesurface 11A of the first insulator 11. The second reverse surface 12Bfaces opposite from the second obverse surface 12A. The second reversesurface 12B is partially exposed.

As shown in FIG. 7, the second insulator 12 is provided with a pluralityof embedded portions 121. The plurality of embedded portions 121protrude from the second obverse surface 12A in the thickness directionz. The plurality of embedded portions 121 are positioned in theplurality of resistive slits 21 of the resistive body 20. In theresistor A10, each of the plurality of embedded portions 121 is incontact with the side walls 22 of the resistive slit 21.

FIG. 8 shows an example where the plurality of embedded portions 121 ofthe second insulator 12, as well as a plurality of embedded portions 111provided for the first insulator 11, are positioned within the pluralityof resistive slits 21 of the resistive body 20. The plurality ofembedded portions 111 protrude from the first obverse surface 11A of thefirst insulator 11 in the thickness direction z. In the resistor A10,each of the plurality of embedded portions 111 is in contact with theside walls 22 of the resistive slit 21 and the embedded portion 121. Inthis way, at least one of the first insulator 11 and the secondinsulator 12 is partially positioned within the resistive slits 21.

The covering body 30 is formed on the first reverse surface 11B of thefirst insulator 11 in the resistor A10, as shown in FIG. 6. The coveringbody 30 includes a first covering body 30A and a second covering body30B. The first covering body 30A refers to the covering body 30 that isformed on the first insulator 11. The second covering body 30B refers tothe covering body 30 that is formed on the second insulator 12. Theresistor A10 includes the first covering body 30A of the covering body30.

As shown in FIGS. 5 and 6, the first covering body 30A (covering body30) has a first layer 31 and a second layer 32. As shown in FIGS. 2 and6, the first layer 31 is in contact with the first reverse surface 11Bof the first insulator 11. The first layer 31 has electricalconductivity. The first layer 31 is made of a material that containscopper. The first layer 31 is preferably made of a material that has arelatively low electrical resistivity and a relatively high thermalconductivity. The first layer 31 has a thickness of 70 μm to 90 μm.Accordingly, the first layer 31 is thicker than each of the firstinsulator 11 and the second insulator 12. As shown in FIGS. 1 and 6, thesecond layer 32 is formed on the first layer 31. The second layer 32 isa synthetic resin sheet that is electrically insulative. The secondlayer 32 may be a synthetic resin sheet made of glass epoxy resin.

As shown in FIGS. 2 and 6, the first layer 31 is provided with a slit311 that extends through in the thickness direction z. The slit 311splits the first layer 31 into multiple areas. In addition, both ends ofthe first layer 31 in the second direction y are partially open. In theresistor A10, the slit 311 is inclined relative to the first directionx, as viewed along the thickness direction z. The slit 311 passesthrough a center C of the first covering body 30A, as viewed along thethickness direction z. The center C of the first covering body 30Arefers to the intersection of the diagonal lines of the first coveringbody 30A, as viewed along the thickness direction z. As shown in FIG. 7,side walls 312 of the slit 311 are recessed toward the inside of thefirst layer 31.

As shown in FIG. 7, the second layer 32 is provided with an embeddedportion 321. The embedded portion 321 protrudes in the thicknessdirection z from the surface of the second layer 32 that is in contactwith the first layer 31. The embedded portion 321 is positioned in theslit 311 of the first layer 31. In this way, the second layer 32 ispartially positioned within the slit 311. In the resistor A10, theembedded portion 321 is in contact with the side walls 312 of the slit311.

As shown in FIG. 6, the pair of electrodes 40 are electrically connectedto the resistive body 20 on both sides in the first direction x. Each ofthe pair of electrodes 40 includes a base layer 40A and a plating layer40B. As shown in FIGS. 6 and 7, in the resistor A10, the base layer 40Ais in contact with the first insulator 11, the resistive body 20, andthe second insulator 12. An example of the base layer 40A is anickel-chromium (Cr) alloy. The plating layer 40B covers the base layer40A. In the resistor A10, the plating layer 40B is a metal layerconsisting of copper, nickel, and tin that are formed in the statedorder from the part that is in contact with the base layer 40A.

As shown in FIGS. 4 to 6, each of the pair of electrodes 40 has a bottomportion 41 and a side portion 42. Each of the bottom portion 41 and theside portion 42 includes the base layer 40A and the plating layer 40B.The bottom portion 41 is positioned opposite from the resistive body 20with respect to the second insulator 12 in the thickness direction z. Asshown in FIG. 4, the bottom portion 41 overlaps with the first obversesurface 11A of the first insulator 11, as viewed along the thicknessdirection z. In the resistor A10, the bottom portion 41 is in contactwith the second reverse surface 12B of the second insulator 12.

As shown in FIGS. 4 to 6, the side portion 42 is connected to the bottomportion 41 and extends in the thickness direction z. As shown in FIG. 7,the resistive body 20 has a pair of first end surfaces 20A facing in thefirst direction x. The pair of side portions 42 are in contact with thepair of first end surfaces 20A. This allows the pair of electrodes 40 toelectrically connect to the resistive body 20. The second insulator 12has a pair of second end surfaces 12C facing in the first direction x.The first insulator 11 has a pair of third end surfaces 11C facing inthe first direction x. The pair of second end surfaces 12C and the pairof third end surfaces 11C are flush with the pair of first end surfaces20A. The pair of side portions 42 are also in contact with the pair ofsecond end surfaces 12C and the pair of third end surfaces 11C.

As shown in FIG. 7, the first covering body 30A has a pair of firstprotrusions 33. The first insulator 11 has a pair of second protrusions113. The pair of first protrusions and the pair of second protrusions113 protrude in the first direction x from the pair of first endsurfaces 20A of the resistive body 20. In the resistor A10, the pair offirst protrusions 33 are formed of the first layer 31 and the secondlayer 32. As shown in FIG. 9, the pair of side portions 42 are incontact with both the pair of first protrusions 33 and the pair ofsecond protrusions 113. The plating layers 40B of the pair of sideportions 42 are in contact with portions, of the pair of firstprotrusions 33, that are formed of the first layer 31.

The following describes an example of a method for manufacturing theresistor A10, with reference to FIGS. 10 to 16. Note that thecross-sectional positions shown in FIGS. 10 to 16 are the same as thecross-sectional position shown in FIG. 6.

First, as shown in FIG. 10, a resistive body 82 and a first coveringlayer 83 are arranged on a first insulator 81. The first insulator 81has an obverse surface 811 and a reverse surface 812 that face oppositefrom each other in the thickness direction z. The first insulator 81,the resistive body 82, and the first covering layer 83 correspond to thefirst insulator 11, the resistive body 20, and the first layer (thefirst covering body 30A) of the resistor A10, respectively. Theresistive body 82 is press-bonded to the obverse surface 811 to bearranged on the first insulator 81. The first covering layer 83 ispress-bonded to the reverse surface 812 to be arranged on the resistivebody 82. The resistive body 82 is provided with a plurality of resistiveslits 821 that extend through in the thickness direction z. The firstcovering layer 83 is provided with a slit 831 that extends through inthe thickness direction z. The plurality of resistive slits 821 and theslit 831 are formed by wet etching.

Next, as shown in FIG. 11, a second insulator 84 is formed on theresistive body 82. The second insulator 84 corresponds to the secondinsulator 12 of the resistor A10. The second insulator 84 ispress-bonded to the resistive body 82 to be formed thereon. This stepallows portions of the second insulator 84 to be positioned within theplurality of resistive slits 821 of the resistive body 82. The step alsoincludes laminating a second covering layer 85 on the first coveringlayer 83. The second covering layer 85 corresponds to the second layer32 (the first covering body 30A) of the resistor A10. The secondcovering layer 85 is press-bonded to the first covering layer 83 to beformed thereon. This step allows a part of the second covering layer 85to be positioned within the slit 831 of the first covering layer 83.

Next, as shown in FIG. 12, a plurality of grooves 881, which arerecessed from the second insulator 84 in the thickness direction z, areformed. The plurality of grooves 881 are formed along the seconddirection y. The plurality of grooves 881 are formed by using a dicingblade, for example. As a result of forming the plurality of grooves 881,respective parts of the second insulator 84, the resistive body 82, andthe first insulator 81 are removed. Out of these elements, the pluralityof grooves 881 extend through the second insulator 84 and the resistivebody 82 in the thickness direction z. Each of the plurality of grooves881 has a width b1 (i.e., the dimension of each groove 881 in the firstdirection x).

Next, as shown in FIG. 13, a base layer 86 is formed to cover thesurfaces of the second insulator 84 and the plurality of grooves 881.The base layer 86 corresponds to the base layers 40A of the pair ofelectrodes 40 in the resistor A10. The base layer 86 is formed by asputtering method.

Next, as shown in FIG. 14, the base layer 86 that covers the surface ofthe second insulator 84 is partially removed. The removal of a part ofthe base layer 86 is achieved by first forming a mask on the base layer86 and then performing wet etching on a part of the base layer 86 thatis not covered with the mask. The second insulator 84 is exposed fromwhere the part of the base layer 86 has been removed.

Next, as shown in FIG. 15, a plurality of slits 882 are formed. Theplurality of slits 882 are formed in a lattice pattern along the firstdirection x and the second direction y. Some of the plurality of slits882, which are along the second direction y, are formed in the thicknessdirection z from the base layer 86 that covers the bottoms of theplurality of grooves 881. The plurality of slits 882 are formed by usinga dicing blade, for example. Each of the plurality of slits 882 has awidth b2 (the dimension of each slit 882 in the first direction x). Thewidth b2 is smaller than the width b1 of each groove 881. With thisstep, the first insulator 81, the resistive body 82 formed on the firstinsulator 81, the first covering layer 83, the second insulator 84, thesecond covering layer 85, and the base layer 86 are divided intoindividual pieces. In other words, forming of the first insulator 11,the second insulator 12, the resistive body 20, the first covering body30A (covering body 30), and the base layers 40A of the pair ofelectrodes 40 of the resistor A10 has been completed.

Finally, as shown in FIG. 16, a pair of plating layers 40B covering thepair of base layers 40A are formed. The pair of plating layers 40B areformed by electrolytic barrel plating. With this step, forming of thepair of electrodes 40 of the resistor A10 has been completed.Furthermore, this step allows the pair of first protrusions 33 of thefirst covering body 30A and the pair of second protrusions 113 of thefirst insulator 11 to be covered with the pair of plating layers 40B.The resistor A10 is manufactured through the above steps.

<First Variation>

With reference to FIG. 17, a resistor A11 according to a first variationof the resistor A10 is described. The resistor A11 is different from theresistor A10 described above in the structures of the first insulator11, the first covering body 30A (covering body 30), and the pair ofelectrodes 40.

Unlike the resistor A10, the first insulator 11 is not provided with thepair of second protrusions 113. The first layer 31 of the first coveringbody 30A has a pair of fourth end surfaces 313 facing in the firstdirection x. The pair of fourth end surfaces 313 are flush with the pairof third end surfaces 11C of the first insulator 11. The pair of fourthend surfaces 313 are in contact with the side portions 42 of the pair ofelectrodes 40.

The pair of first protrusions 33 of the first covering body 30A areformed of the first layer 31 and the second layer 32. Parts of the pairof first protrusions 33 that are formed of the first layer 31 protrudein the first direction x from the pair of fourth end surfaces 313. Theside portions 42 of the pair of electrodes 40 are in contact with theparts, of the pair of first protrusions 33, that are formed of the firstlayer 31.

The structure of the resistor A11 is obtained by forming, during thestep of forming the plurality of grooves 881 shown in FIG. 12, theplurality of grooves 881 to be deeper than the plurality of grooves 881formed in the manufacturing of the resistor A10.

<Second Variation>

With reference to FIG. 18, a resistor A12 according to a secondvariation of the resistor A10 is described. The resistor A12 isdifferent from the resistor A10 described above in the structures of thefirst insulator 11, the first covering body 30A (covering body 30), andthe pair of electrodes 40.

Unlike the resistor A10, the first insulator 11 is not provided with thepair of second protrusions 113. The first layer 31 of the first coveringbody 30A has a pair of fourth end surfaces 313 facing in the firstdirection x. The dimension of each of the pair of fourth end surfaces313 in the thickness direction z is larger than the dimension of each ofthe pair of fourth end surfaces 313 of the resistor A11. The pair offourth end surfaces 313 are in contact with the side portions 42 of thepair of electrodes 40.

The pair of first protrusions 33 of the first covering body 30A areformed of the second layer 32. The side portions 42 of the pair ofelectrodes 40 are in contact with the pair of first protrusions 33 thatare formed of the second layer 32.

The structure of the resistor A12 is obtained by forming, during thestep of forming the plurality of grooves 881 shown in FIG. 12, theplurality of grooves 881 to be deeper than the plurality of grooves 881formed in the manufacturing of the resistor A11.

<Third Variation>

With reference to FIG. 19, a resistor A13 according to a third variationof the resistor A10 is described. The resistor A13 is different from theresistor A10 described above in the structure of the first layer 31 ofthe first covering body 30A (covering body 30).

In the resistor A13, the slit 311 of the first layer 31 is inclinedrelative to the first direction x, as viewed along the thicknessdirection z. The slit 311 passes through the center C of the firstcovering body 30A and is bent at the center C, as viewed along thethickness direction z. Accordingly, the direction of inclination of theslit 311 relative to the first direction x is reversed at the center C.Although not shown in figures, the side walls 312 of the slit 311 arealso recessed toward the inside of the first layer 31.

<Fourth Variation>

With reference to FIG. 20, a resistor A14 according to a fourthvariation of the resistor A10 is described. The resistor A14 isdifferent from the resistor A10 described above in the structure of thefirst layer 31 of the first covering body 30A (covering body 30).

In the resistor A14, the slit 311 of the first layer 31 has a first slit311A and a plurality of second slits 311B, as viewed along the thicknessdirection z. The first slit 311A extends in the first direction x. Theplurality of second slits 311B are connected to the respective ends ofthe first slit 311A in the first direction x, and extend in the seconddirection y. Accordingly, the slit 311 has a crank shape as viewed alongthe thickness direction z. The first slit 311A passes through the centerC of the first covering body 30A, as viewed along the thicknessdirection z. Although not shown in figures, the side walls 312 of theslit 311 in the resistor A14 are also recessed toward the inside of thefirst layer 31.

<Fifth Variation>

With reference to FIG. 21, a resistor A15 according to a fifth variationof the resistor A10 is described. The resistor A15 is different from theresistor A10 described above in the structure of the first layer 31 ofthe first covering body 30A (covering body 30).

In the resistor A15, the slit 311 of the first layer 31 extends in thesecond direction y, as viewed along the thickness direction z. The slit311 passes through the center C of the first covering body 30A, asviewed along the thickness direction z. Although not shown in figures,the side walls 312 of the slit 311 in the resistor A15 are also recessedtoward the inside of the first layer 31.

The following describes advantages of the resistor A10.

The resistor A10 includes the first covering body 30A (covering body 30)formed on the first insulator 11. The first covering body 30A has thefirst layer 31 that is in contact with the first insulator 11. The firstlayer 31 has electrical conductivity. As such, heat generated from theresistive body 20 during the use of the resistor A10 flows through boththe first insulator 11 and the second insulator 12. The heat that hasflowed through the first insulator 11 flows through the first coveringbody 30A. Since the first covering body 30A has the first layer 31, thefirst covering body 30A has a higher thermal conductivity than each ofthe first insulator 11 and the second insulator 12. As a result, heatgenerated from the resistive body 20 easily flows through the firstcovering body 30A. The heat that has flowed through the first coveringbody 30A is released to the outside of the resistor A10. Accordingly,the resistor A10 can improve heat dissipation property.

The first layer 31 is provided with the slit 311 that extends through inthe thickness direction z. The first layer 31 is divided into aplurality of areas by the slit 311. The first layer 31 has a higherthermal expansion coefficient than each of the first insulator 11, thesecond insulator 12, and the resistive body 20. As such, when heat isgenerated from the resistive body 20, thermal stress tends to beconcentrated between the first insulator 11 and the first covering body30A. Too much concentration of the thermal stress causes a warp to beformed in the resistor A10 relative to the thickness direction z. Theslit 311 in the first layer 31 can alleviate the thermal stress betweenthe first insulator 11 and the first covering body 30A.

The first covering body 30A is provided with the pair of firstprotrusions 33 protruding from the pair of first end surfaces 20A of theresistive body 20 in the first direction x. Each of the pair of firstprotrusions 33 may be formed of both the first layer 31 and the secondlayer 32 as seen in the resistor A10 (see FIG. 9) and the resistor A11(see FIG. 17), or may be formed of the second layer 32 as seen in theresistor A12 (see FIG. 18). In either case, the pair of electrodes 40are electrically connected to the first layer 31 by the side portions 42of the pair of electrodes 40 being in contact with the pair of firstprotrusions 33. Accordingly, it is possible to prevent a short circuitbetween the pair of electrodes 40 by providing the slit 311 in the firstlayer 31.

The first layer 31 is made of a material that contains copper. Copperhas a relatively high thermal conductivity and a relatively low electricresistivity. This further improves the heat dissipation property of theresistor A10. Furthermore, it is possible to reduce variations in theresistance of the resistor A10 caused by the pair of electrodes 40 beingin contact with the first layer 31.

The first insulator 11 contains the fillers 112 that are electricallyinsulative. The fillers 112 can further improve the mechanical strengthof the first insulator 11. Also, the fillers 112 are made of a materialcontaining ceramics having a relatively high thermal conductivity. Thisfurther increases the thermal conductivity of the first insulator 11.Accordingly, heat generated from the resistive body 20 can betransferred in a larger amount to the first covering body 30A via thefirst insulator 11, and this further improves the heat dissipationproperty of the resistor A10.

The first covering body 30A has the second layer 32 that is formed onthe first layer 31 and electrically insulative. This can protect thefirst layer 31 and prevent a current from leaking outside the firstlayer 31. A part of the second layer 32 is positioned within the slit311 of the first layer 31. This increases the area of contact betweenthe second layer 32 and the first layer 31, thus improving the bondingstrength of the second layer 32 to the first layer 31.

The side walls 312 of the slit 311 in the first layer 31 are recessedtoward the inside of the first layer 31. This allows the slit 311 toproduce an anchoring effect with respect to the second layer 32, thusfurther improving the bonding strength of the second layer 32 to thefirst layer 31.

The resistive body 20 is provided with the plurality of resistive slits21 that extend through in the thickness direction z. At least part ofthe first insulator 11 or the second insulator 12 are positioned withinthe resistive slits 21. As a result, the area of contact between theresistive body 20 and at least one of the first insulator 11 and thesecond insulator 12 increases, thus improving the bonding strength ofthe at least one of the first and second insulators 11, 12 to theresistive body 20.

The side walls 22 of the resistive slits 21 of the resistive body 20 arerecessed toward the inside of the resistive body 20. This allows theresistive slits 21 to produce an anchoring effect with respect to atleast one of the first insulator 11 and the second insulator 12, thusfurther improving the bonding strength of the at least one of the firstand second insulators 11, 12 to the resistive body 20.

Each of the pair of electrodes 40 has the side portion 42 that isconnected to the bottom portion 41 and that extends in the thicknessdirection z. The pair of side portions 42 are in contact with the pairof first end surfaces 20A of the resistive body 20, the pair of secondend surfaces 12C of the second insulator 12, and the pair of third endsurfaces 11C of the first insulator 11. The pair of second end surfaces12C and the pair of third end surfaces 11C are flush with the pair offirst end surfaces 20A. Accordingly, in the resistive body 20, only thepair of first end surfaces 20A are in contact with the pair ofelectrodes 40. The pair of first end surfaces 20A have the same size.This suppresses variations in the resistance of the resistor A10.

Second Embodiment

With reference to FIGS. 22 to 23, a resistor A20 according to a secondembodiment of the present disclosure will be described. In thesefigures, elements that are the same as or similar to the elements of theresistor A10 described above are provided with the same reference signs,and descriptions thereof are omitted. Note that the cross-sectionalposition shown in FIG. 22 is the same as the cross-sectional positionshown in FIG. 6.

The resistor A20 is different from the resistor A10 described above inthe structures of the first insulator 11, the second insulator 12, thecovering body 30, and the pair of electrodes 40.

As shown in FIG. 23, the second insulator 12 contains fillers 122 thatare electrically insulative. The fillers 122 are made of the samematerial as the fillers 112 contained in the first insulator 11 of theresistor A10 described above. Note that the first insulator 11 of theresistor A20 does not contain any fillers 112.

As shown in FIG. 22, the covering body 30 is formed on the secondreverse surface 12B of the second insulator 12. As such, the resistorA20 includes the second covering body 30B of the covering body 30.

As shown in FIG. 22, the second covering body 30B has a first layer 31and a second layer 32, as with the first covering body 30A. The firstlayer 31 is in contact with the second reverse surface 12B of the secondinsulator 12. The first layer 31 has electrical conductivity. The firstlayer is made of a material that contains copper. The first layer 31 ispreferably made of a material that has a relatively low electricalresistivity and a relatively high thermal conductivity. The second layer32 is formed on the first layer 31. The second layer 32 is a syntheticresin sheet that is electrically insulative. One example of thesynthetic resin sheet contains glass epoxy resin.

As shown in FIG. 23, the first layer 31 is provided with a slit 311 thatextends through in the thickness direction z. The slit 311 splits thefirst layer 31 into multiple areas. The slit 311 may have any shapeselected from the slits in the resistor A10 (see FIG. 2), the resistorA13 (see FIG. 19), the resistor A14 (see FIG. 20), and the resistor A15(see FIG. 21). The side walls 312 of the slit 311 are recessed towardthe inside of the first layer 31.

As shown in FIG. 23, the second layer 32 is provided with an embeddedportion 321. The embedded portion 321 protrudes in the thicknessdirection z from the surface of the second layer 32 that is in contactwith the first layer 31. The embedded portion 321 is positioned in theslit 311 of the first layer 31. In this way, the second layer 32 ispartially positioned within the slit 311. In the resistor A20, theembedded portion 321 is in contact with the side walls 312 of the slit311.

As shown in FIG. 23, the first layer 31 has a pair of fourth endsurfaces 313. The pair of fourth end surfaces 313 face in the firstdirection x. The second layer 32 has a pair of fifth end surfaces 322.The pair of fifth end surfaces 322 face in the first direction x. Thepair of fourth end surfaces 313 and the pair of fifth end surfaces 322are flush with the pair of first end surfaces 20A of the resistive body20. In the resistor A20, the second covering body 30B is not providedwith the pair of first protrusions 33.

As shown in FIGS. 22 and 23, the bottom portions 41 of the pair ofelectrodes 40 are in contact with the second layer 32 of the secondcovering body 30B. As shown in FIG. 23, the side portions 42 of the pairof electrodes 40 are in contact with the pair of first end surfaces 20Aof the resistive body 20, the pair of second end surfaces 12C of thesecond insulator 12, and the pair of third end surfaces 11C of the firstinsulator 11. Furthermore, the pair of side portions 42 are in contactwith the pair of fourth end surfaces 313 of the first layer 31 and thepair of fifth end surfaces 322 of the second layer 32. The pair of sideportions 42 are in contact with the pair of second protrusions 113 ofthe first insulator 11.

The following describes advantages of the resistor A20.

The resistor A20 includes the second covering body 30B (covering body30) formed on the second insulator 12. The second covering body 30B hasthe first layer 31 that is in contact with the second insulator 12. Thefirst layer 31 has electrical conductivity. As such, heat generated fromthe resistive body 20 during the use of the resistor A20 flows throughboth the first insulator 11 and the second insulator 12. The heat thathas flowed through the second insulator 12 flows through the secondcovering body 30B. Since the second covering body 30B has the firstlayer 31, the second covering body 30B has a higher electricalconductivity than each of the first insulator 11 and the secondinsulator 12. As a result, heat generated from the resistive body 20easily flows through the second covering body 30B. The heat that hasflowed through the second covering body 30B is released to the outsideof the resistor A20. Accordingly, the resistor A20 can also improve heatdissipation property.

The second insulator 12 contains the fillers 122 that are electricallyinsulative. The fillers 122 can further improve the mechanical strengthof the second insulator 12. Also, the fillers 122 are made of a materialcontaining ceramics having a relatively high thermal conductivity. Thisfurther increases the thermal conductivity of the second insulator 12.Accordingly, heat generated from the resistive body 20 can betransferred in a larger amount to the second covering body 30B via thesecond insulator 12, and this further improves the heat dissipationproperty of the resistor A20.

The bottom portions 41 of the pair of electrodes 40 are in contact withthe second layer 32 of the second covering body 30B. As a result, heatgenerated from the resistive body 20 and transferred to the secondcovering body 30B via the second insulator 12 can be quickly dissipatedto the outside of the resistor A20 by means of the pair of electrodes40.

Third Embodiment

With reference to FIGS. 24 to 25, a resistor A30 according to a thirdembodiment of the present disclosure will be described. In thesefigures, elements that are the same as or similar to the elements of theresistor A10 described above are provided with the same reference signs,and descriptions thereof are omitted. Note that the cross-sectionalposition shown in FIG. 24 is the same as the cross-sectional positionshown in FIG. 6.

The resistor A30 is different from the resistor A10 described above inthe structures of the second insulator 12, the covering body 30, and thepair of electrodes 40.

As shown in FIG. 25, the second insulator 12 contains fillers 122 thatare electrically insulative. The fillers 122 are made of the samematerial as the fillers 112 contained in the first insulator 11 of theresistor A10 described above.

As shown in FIG. 24, the covering body 30 is formed on each of the firstreverse surface 11B of the first insulator 11 and the second reversesurface 12B of the second insulator 12. As such, the resistor A30includes both the first covering body 30A and the second covering body30B of the covering body 30. The first covering body 30A of the resistorA30 has the same structure as the first covering body 30A of theresistor A10, and the second covering body 30B of the resistor A30 hasthe same structure as the second covering body 30B of the resistor A20.Thus, descriptions of the first covering body 30A and the secondcovering body 30B are omitted.

As shown in FIGS. 24 and 25, the bottom portions 41 of the pair ofelectrodes 40 are in contact with the second layer 32 of the secondcovering body 30B. As shown in FIG. 25, the side portions 42 of the pairof electrodes 40 are in contact with the pair of first end surfaces 20Aof the resistive body 20, the pair of second end surfaces 12C of thesecond insulator 12, and the pair of third end surfaces 11C of the firstinsulator 11. Furthermore, the pair of side portions 42 are in contactwith the pair of fourth end surfaces 313 of the first layer 31 and thepair of fifth end surfaces 322 of the second layer 32. The pair of sideportions 42 are in contact with both the pair of first protrusions 33 ofthe first covering body 30A and the pair of second protrusions 113 ofthe first insulator 11. The resistor A30 can also have the samestructure as each of the resistor A11 (see FIG. 17) and the resistor A12(see FIG. 18).

The following describes advantages of the resistor A30.

The resistor A30 includes the first covering body 30A (covering body 30)formed on the first insulator 11, and the second covering body 30B(covering body 30) formed on the second insulator 12. The first coveringbody 30A has the first layer 31 that is in contact with the firstinsulator 11. The second covering body 30B has the first layer 31 thatis in contact with the second insulator 12. The first layer 31 haselectrical conductivity. As such, heat generated from the resistive body20 during the use of the resistor A30 flows through both the firstinsulator 11 and the second insulator 12 to the first covering body 30Aand the second covering body 30B. Since the first covering body 30A andthe second covering body 30B have the respective first layers 31, thefirst covering body 30A and the second covering body 30B have higherconductivities than the first insulator 11 and the second insulator 12.As a result, heat generated from the resistive body 20 easily flowsthrough the first covering body 30A and the second covering body 30B.The heat that has flowed through the first covering body 30A and thesecond covering body 30B is released to the outside of the resistor A30.Accordingly, the resistor A30 can also improve heat dissipationproperty.

Fourth Embodiment

With reference to FIGS. 26 to 29, a resistor A40 according to a fourthembodiment of the present disclosure will be described. In thesefigures, elements that are the same as or similar to the elements of theresistor A10 described above are provided with the same reference signs,and descriptions thereof are omitted. For convenience of understanding,FIG. 26 is shown through the second layer 32 of the covering body 30.

The resistor A40 is different from the resistor A10 described above inthe dimensions of the components and the structures of the pair ofelectrodes 40.

The first insulator 11, the resistive body 20, the second insulator 12,the covering body 30, and the pair of electrodes 40 that constitute theresistor A40 have the same dimensions as the corresponding components ofthe resistor A10 in the first direction x and the second direction y.However, as can be seen in FIGS. 26 to 28, these components of theresistor A40 have smaller dimensions than the corresponding componentsof the resistor A10 in the thickness direction z. The resistor A40 iscloser to the actual product in dimensions than the resistor A10.Furthermore, the number of resistive slits 21 of the resistive body 20is larger than the number of resistive slits 21 of the resistor A10.

As shown in FIGS. 28 and 29, the side portions 42 of the pair ofelectrodes 40 are in contact with the second layer 32 of the firstcovering body 30A (covering body 30). As shown in FIG. 29, the pair offirst protrusions 33 of the first covering body 30A have largerdimensions than the corresponding protrusions in the resistor A10 in thefirst direction x. Furthermore, the pair of second protrusions 113 ofthe first insulator 11 have larger dimensions than the correspondingprotrusions in the resistor A10 in the first direction x.

The present disclosure is not limited to the foregoing embodiments.Various design changes can be made to the specific structures of theelements of the present disclosure.

Various embodiments of the present disclosure can be defined as thefollowing clauses.

Clause 1. A resistor comprising:

a first insulator including an obverse surface facing in a thicknessdirection;

a resistive body provided on the obverse surface;

a second insulator covering the resistive body;

a pair of electrodes electrically connected to the resistive body atboth sides in a first direction perpendicular to the thicknessdirection; and

a covering body formed on at least one of the first insulator and thesecond insulator,

wherein the covering body includes an electroconductive first layer heldin contact with at least one of the first insulator and the secondinsulator.

Clause 2. The resistor according to clause 1, wherein the first layer isprovided with a slit extending through in the thickness direction, and

the first layer is divided into a plurality of areas by the slit.

Clause 3. The resistor according to clause 2, wherein the slit isinclined relative to the first direction, as viewed along the thicknessdirection.

Clause 4. The resistor according to clause 2, wherein as viewed alongthe thickness direction, the slit includes: a first slit extending inthe first direction; and a plurality of second slits extending in asecond direction perpendicular to the thickness direction and the firstdirection.

Clause 5. The resistor according to any of clauses 2 to 4, wherein thefirst layer is made of a material that contains copper.

Clause 6. The resistor according to any of clauses 2 to 5, wherein atleast one of the first insulator and the second insulator containsfillers that are electrically insulative, and

the fillers are made of a material containing ceramics.

Clause 7. The resistor according to any of clauses 2 to 6, wherein thecovering body includes a second layer that is formed on the first layerand electrically insulative, and

a part of the second layer is disposed in the slit.

Clause 8. The resistor according to clause 7, wherein side walls of theslit are recessed toward an inside of the first layer.

Clause 9. The resistor according to clause 7 or 8, wherein the resistivebody is provided with a resistive slit that extends through in thethickness direction, and

at least one of the first insulator and the second insulator is disposedin the resistive slit.

Clause 10. The resistor according to clause 9, wherein side walls of theresistive slit are recessed toward an inside of the resistive body.

Clause 11. The resistor according to any of clauses 7 to 10, whereineach of the pair of electrodes includes a bottom portion and a sideportion, the bottom portion is opposite from the resistive body withrespect to the second insulator in the thickness direction, and overlapswith the obverse surface as viewed along the thickness direction, theside portion is connected to the bottom portion of a corresponding oneof the pair of electrodes, and extends in the thickness direction, theresistive body includes a pair of first end surfaces facing in the firstdirection, and the side portion of each of the pair of electrodes is incontact with one of the pair of first end surfaces.

Clause 12. The resistor according to clause 11, wherein the secondinsulator includes a pair of second end surfaces, each of the pair ofsecond end surfaces facing in the first direction and being flush withone of the pair of first end surfaces, and

the side portion of each of the pair of electrodes is in contact withone of the pair of second end surfaces.

Clause 13. The resistor according to clause 12, wherein the firstinsulator includes a pair of third end surfaces, each of the pair ofthird end surfaces facing in the first direction and being flush withone of the pair of first end surfaces, and

the side portion of each of the pair of electrodes is in contact withone of the pair of third end surfaces.

Clause 14. The resistor according to any of clauses 11 to 13, whereinthe covering body includes a first covering body formed on the firstinsulator,

the first covering body includes a pair of first protrusions separatedfrom each other in the first direction and protruding from the pair offirst end surfaces in the first direction, and

the side portion of each of the pair of electrodes is in contact withone of the pair of first protrusions.

Clause 15. The resistor according to clause 14, wherein the pair offirst protrusions are formed of the second layer of the first coveringbody.

Clause 16. The resistor according to clause 14, wherein the firstinsulator includes a pair of second protrusions separated from eachother in the first direction and protruding from the pair of first endsurfaces in the first direction, and

the side portion of each of the pair of electrodes is in contact withboth one of the pair of first protrusions and one of the pair of secondprotrusions.

Clause 17. The resistor according to any of clauses 14 to 16, whereinthe covering body further includes a second covering body formed on thesecond insulator, and

the bottom portions of the pair of electrodes are in contact with thesecond layer of the second covering body.

1. A resistor comprising: a first insulator including an obverse surfacefacing in a thickness direction; a resistive body provided on theobverse surface; a second insulator covering the resistive body; a pairof electrodes electrically connected to the resistive body at both sidesin a first direction perpendicular to the thickness direction; and acovering body formed on at least one of the first insulator and thesecond insulator, wherein the covering body includes anelectroconductive first layer held in contact with at least one of thefirst insulator and the second insulator.
 2. The resistor according toclaim 1, wherein the first layer is provided with a slit extendingthrough in the thickness direction, and the first layer is divided intoa plurality of areas by the slit.
 3. The resistor according to claim 2,wherein the slit is inclined relative to the first direction as viewedalong the thickness direction.
 4. The resistor according to claim 2,wherein as viewed along the thickness direction, the slit includes: afirst slit extending in the first direction; and a plurality of secondslits extending in a second direction perpendicular to the thicknessdirection and the first direction.
 5. The resistor according to claim 2,wherein the first layer is made of a material that contains copper. 6.The resistor according to claim 2, wherein at least one of the firstinsulator and the second insulator contains fillers that areelectrically insulative, and the fillers are made of a materialcontaining ceramics.
 7. The resistor according to claim 2, wherein thecovering body includes a second layer that is formed on the first layerand electrically insulative, and a part of the second layer is disposedin the slit.
 8. The resistor according to claim 7, wherein side walls ofthe slit are recessed toward an inside of the first layer.
 9. Theresistor according to claim 7, wherein the resistive body is providedwith a resistive slit that extends through in the thickness direction,and at least one of the first insulator and the second insulator isdisposed in the resistive slit.
 10. The resistor according to claim 9,wherein side walls of the resistive slit are recessed toward an insideof the resistive body.
 11. The resistor according to claim 7, whereineach of the pair of electrodes includes a bottom portion and a sideportion, the bottom portion is opposite from the resistive body withrespect to the second insulator in the thickness direction, and overlapswith the obverse surface as viewed along the thickness direction, theside portion is connected to the bottom portion of a corresponding oneof the pair of electrodes, and extends in the thickness direction, theresistive body includes a pair of first end surfaces facing in the firstdirection, and the side portion of each of the pair of electrodes is incontact with one of the pair of first end surfaces.
 12. The resistoraccording to claim 11, wherein the second insulator includes a pair ofsecond end surfaces, each of the pair of second end surfaces facing inthe first direction and being flush with one of the pair of first endsurfaces, and the side portion of each of the pair of electrodes is incontact with one of the pair of second end surfaces.
 13. The resistoraccording to claim 12, wherein the first insulator includes a pair ofthird end surfaces, each of the pair of third end surfaces facing in thefirst direction and being flush with one of the pair of first endsurfaces, and the side portion of each of the pair of electrodes is incontact with one of the pair of third end surfaces.
 14. The resistoraccording to claim 11, wherein the covering body includes a firstcovering body formed on the first insulator, the first covering bodyincludes a pair of first protrusions separated from each other in thefirst direction and protruding from the pair of first end surfaces inthe first direction, and the side portion of each of the pair ofelectrodes is in contact with one of the pair of first protrusions. 15.The resistor according to claim 14, wherein the pair of firstprotrusions are formed of the second layer of the first covering body.16. The resistor according to claim 14, wherein the first insulatorincludes a pair of second protrusions separated from each other in thefirst direction and protruding from the pair of first end surfaces inthe first direction, and the side portion of each of the pair ofelectrodes is in contact with both one of the pair of first protrusionsand one of the pair of second protrusions.
 17. The resistor according toclaim 14, wherein the covering body further includes a second coveringbody formed on the second insulator, and the bottom portions of the pairof electrodes are in contact with the second layer of the secondcovering body.
 18. The resistor according to claim 3, wherein the firstlayer is made of a material that contains copper.
 19. The resistoraccording to claim 4, wherein the first layer is made of a material thatcontains copper.
 20. The resistor according to claim 3, wherein at leastone of the first insulator and the second insulator contains fillersthat are electrically insulative, and the fillers are made of a materialcontaining ceramics.